This invention relates generally to packages for optical modules and, particularly, to packages that receive an optical fiber and provide electrical connections thereto.
Standard techniques to carry an electrical signal across the wall of a package for optical modules include multi-layer ceramic inserts. Standard ceramic designs for optical modules, commonly called butterfly packages, may include a base, a fiber feed through, a can body, and a ring frame made of metal, as well as one or more multi-layer ceramic inserts that receive electrical connectors. A lid is typically used to hermetically close the package by welding or soldering to a ring frame.
The ceramic inserts may be composed of multi-layer ceramic. The inserts typically carry direct current or low frequency electrical signals. An insert may include a base ceramic layer, a plated bottom, and a patterned plating on the top surface. A narrower ceramic layer or top layer is attached to the base ceramic layer in a way that creates two shelves. An outside shelf allows electrical leads to be soldered to the package and an inside shelf allows an electrical signal to be accessible from inside the package. The inside shelf typically receives wire bonds that further carry the signal to or from the circuitry mounted inside the package.
The ceramic inserts may be fitted and soldered between the body and the ring frame forming a hermetic seal. Usually, the ceramic insert is wider than the surrounding body and the ring frame. This ensures good hermetic soldering between the plated ceramic surfaces and the metal body and frame. As the metal wall thickness is reduced, the wall thickness of the ceramic inserts may be reduced as well. However, reliability issues start to appear as the ceramic thickness decreases and stress concentration increases. This minimum wall thickness dictates the minimum overall insert width and, therefore, the minimum size of the package.
Thus, there is a need for a way to make inserts for optical module packages that have substantial ceramic wall thicknesses with reduced overall width.